Low molecular weight linear alkyl benzene sulfonate as frothing agents for gypsum board manufacture

ABSTRACT

THIS INVENTION RELATES TO GYPSUM BOARDS AND TO A METHOD FOR PRODUCING THE BOARD WHICH UTILIZES AS A FROTHING AGENT AND ALKYL BENZENE SULFONATE HAVING A LINEAR SECONDARY ALKYL SIDE CHAIN WITH AN AVERAGE CARBON CONTENT RANGING FROM 8.5 TO 10.5 AND A MAXIMUM CARBON NUMBER SPREAD OF 8 CARBON ATOMS. PREFERABLY, THE AVERAGE CARBON CONTENT RANGES FROM 9.5 TO 10.5 AND THE CARBON NUMBER SPRAD IS A MAXIMUM OF 5 CARBON ATOMS. THIS FROTHING AGENT IS GENERALLY UTILIZED IN AMOUNTS RANGING FROM 0.01 TO 0.1 PART PER 100 PARTS BY WEIGHT GYPSUM.

United States Patent 3,577,248 LOW MOLECULAR WEIGHT LINEAR ALKYL BEN- ZENE SULFONATE AS FROTHING AGENTS FOR ABSTRACT OF THE DISCLOSURE This invention relates to gypsum boards and to a meth- 0:1 for producing the board which utilizes as a frothing agent an alkyl benzene sulfonate having a linear secondary alkyl side chain with an average carbon content rangingfrom 8.5 to 10.5 and a maximum carbon number spread of 8 carbon atoms. Preferably, the average carbon content ranges from 9.5 to 10.5 and the carbon number spread is a maximum of carbon atoms. This frothing agent is generally utilized in amounts ranging from 0.01 to 0.1 part per 100 parts by weight gypsum.

BACKGROUND OF INVENTION core to lower the density of'the final board. This is accomplished by incorporating a froth or foam into the 'slurry'priorto" the evaporationof water. The froth is prepared by agitating an aqueous solution of a frothing agent such as rosin soap. Attempts have been made to utilize in commercial operations synthetic detergents such as alkyl benzene sulfonates having alkyl side chains containing from 11 to 13 carbon atoms which have been very successful in other fields such as dishwashing and clothes washing. It was found, however, that the amount and stability of the foam generated by these frothing agents was not sufficient to insure uniform low density throughout the board.

It has now been discovered that alkyl benzene sulfonates having a linear secondary alkyl side chain with an average carbon content ranging from 8.5 to 10.5 and a maximum carbon numberspread of eight carbon atoms is superior to other alkyl benzene sulfonates in producing greater amounts of more stable foam in the gypsum slurry. This phenomenon is unexpected since it is well-known in the art that in other detergent applications alkyl benzene sulfonates having alkyl chains of less than eleven carbon atom exhibit poorer detergent properties including foam generation and stability. Because of the outstanding stability a substantial portion of the foam remains intact during the agitation and setting of the gypsum slurry in the gypsum. board thus permitting the utilization of smaller amounts of foam and consequentdly lower frothing agent loadings. V v

It is an object of this invention to provide an improved method of producing gypsum board.

Patented May 4, 1971 It is a further object of this invention to provide a new light weight gypsum board having uniform density characteristics.

The alkyl benzene sulfonates which can be utilized in the practice of this invention have the following structural formula wherein R and R are linear alkyl radicals and the average carbon content of the sum of R and R ranges from 7.5 to 9.5. X is an alkali metal ion or ammonium. It has been found that while alkyl benzene sulfonates wherein R+R' ranges from 7.5 to 8.5 impart uniform density to the board their efiiciency is impaired by the presence of certain accelerators or retarders such as starch. Preferably, therefore, the average carbon content resulting from the sum of R+R' ranges from 8.5 to 9.5 and the maximum carbon number spread is five. The most suitable salt is that in which sodium is the cation.

The alkyl benzene sulfonates of this invention can be prepared by subjecting a linear olefin or a secondary linear alkyl chloride or alcohol and benzene to an alkylation environment in the presence of an alkylation catalyst such as AlCl HF, H 80 or BF The alkylated benzene can then be sulfonated utilizing re-agents such as sulfuric acid, sulfur trioxide or oleum. The sulfonated portion of the molecule is then neutralized by reaction with an alkali metal compound such as sodium hydroxide or an ammonium compound such as ammonia or ammonium hydroxide.

The light weight gypsum boards of this invention can be prepared by placing a froth-containing gypsum slurry between two impervious barries and then evaporating the free water to allow the gypsum to set. The slurry is pre- 40 pared by adding gypsum to water and agitating. The

amount of water will vary depending upon the type of gypsum and the strength and density of the desired board. Generally, the water ranges from 60 to 130 parts per 100 parts gypsum. The froth can be generated in the slurry by merely adding a frothing agent and then agitating the mixture until the desired level of foam is produced. Preferably, however, the foam is first prepared and then added to the slurry. The amount of frothing agent utilized depends ultimately upon the desired density of the board.

Other factors which dictate the proper frothing agent loading include the type of gypsum, the hardness of the water and the specific foaming properties of the frothing agent. For most commercial operations the amounts of frothing agent ranges from 0.001 to 1 part per 100 parts gypsum.

Optimum loadings are usually in the range of 0.01 to 0.1

part per 100 parts gypsum.

After depositing the slurry between two impervious barriers such as paper sheets, the mixture is then subjected to heat usually at about 250 F. to 350 F. to evaporate the water and allow the gypsum to set. Additional components such as builders or stabilizers can be added to the froth to enhance or increase its basic properties. Various commercial methods of producing gypsum board are wellknown in the art as exemplified by U.S. Pat. Nos. 2,560,-

521; 2,432,963; 2,207,339 and 3,343,818 which are here- 1 by incorporated by reference into this specification.

Various additives can also be utilized to aid in the setting. For example, accelerators such as ground gypsum, potassium sulfate or ammonium sulfate can be added to TABLE I Formulation No 1 2 3 4 5 6 7 improve setting rates. Additives such as starch or glue A t l 33 1 0 .4 9.5 10.3 10.4 11.3 13.0

i O 113. a y 0 1103.! 011 can be addedto retard setting at the surface of barriers mlge 840 (1) 940 941 9% (2) 1H4 and thus provide a better core-to-barrier bond. Structural Maximum carbon sp 3 12 2 3 5 4 3 Time (sec.) to generate elements such as fibers or ground paper can also be inspecified amounts corporated to alter the strength characteristics of the final 88 3; 12 $3 15 1% 120 600 cc... 2 18 board. Most add tives are utilized in amounts ranging 700 com 44 56 31 34 from 0.1 to 2 parts per 100 parts gypsum. T tSiJif) cc ..a.fE...1.2.6 120 120 94 64 The following examples are given to illustrate specific 2.20.1311? 800 750 815 900 850 610 350 embodiments of this invention and should not be cong fig sf after strued as limitations upon the scope of invention. All 1min g g 3 g fig parts are by weight. All alkyl benzene sulfonates utilized 4e 35 e0 29 34 50 147 m the examples Were fl:1e Sodmm salts- 1 A blend of 22% sodium xylene sulfonate and 78% of 010-013 linear The foam tests utilized in these examples have been gx g fgg g gfifi f found by empirical correlation to provide an accurate (a) parts OfaCs-Cm alkcxylated straight chain alcohol having an average of 10-12 alkoxyl units of which three fourths are ethoxy indication of the suitability of various frothing agents in 20 g) your? i propoxy, 1 I C C r d 8 par s 0 an aqueous so 11 ion 0 a 10- 13 inear seco a y contmercla'l profluctlon of gypsum board f gen alkyl benzene sulfonate wherein the solids content of the solution is eration versus time test demonstrates the ability of the y frothing agent to be utilized as an in situ foam generation F 3 1, E 4 and 5 Whlchf retpreseltlt embodl source or in the independent generation of foam at speeds ments 0 1S mvennon genefate. at a as er m e an aver- Whi h m tch th I t f sum slurr in ut The total age of 47% more foam which is 53% more stable than c a '1 a e O gyp P h the average of those produced by Formulations 2, 6 and foam genefated 1s Pleasure of w efllmencyPft e f f 7 which are outside the scope of this invention. ng agent in generating f oam lvighich ilictatesfits fleasibihty EXAMPLE H a m commercla fioper atlor l 2 i H :ffi The following example was conducted in accordance rated after spec} ed tune mterv S m ca es t 6 Sta 1 lty with the procedure set forth in Example I. The formula- Of the foam Whlch to Prevent collapse of board must tions were prepared using water of 500 ppm. hardness remain intact until the gypsum has set sufliciently. at F.

TABLE II Formulation No 8 9 10 11 12 13 14 15 Average No. of carbons in alkyl chain 9.0 9. 9.5 10.3 10.4 11.3 13.0 Actual alkyl chain carbon range.-. 89 8-10 9-10 9-11 913 10-13 12-14 Maximum carbon spread 2 3 1 2 3 5 4 Time (sec.) to generate specified amounts of team:

15 14 15 19 110 120 22 76 20 21 40 120 32 46 115 100 95 800 620 800 825 Volume (00.) of water after X minutes:

As defined in Table I.

EXAMPLE I Frothing formulations were prepared utilizing 0.062% of the sodium salt of linear secondary alkyl benzene sulfonates in water of 100 ppm. hardness at 40 F. The carbon structures of the alkyl side chains are described in Table I. 160 cc. of each formulation was placed in a graduated cylinder and agitated on a Hamilton Beach #33 mixer. The time necessary to generate specific amounts of foam were noted. After 120 seconds the foam was transferred to a one liter graduated cylinder and the volume of drained water was recorded at various times. made.

TABLE III Formulation No 16 17 18 19 20 21 22 23 Average No. of carbons in alkyl chain 9. 0 9. 4 10. 0 10.3 10. 4 11. 3 11. 3 Actual alkyl chain carbon range... 8-9 8-10 9-11 9-13 10-13 Maximum carbon spread 3 1 8 3 5 Time (sec.) to generate specified amounts of foam:

500 cc 14 15 120 41 28 32 120 120 600 ce 21 27 120 700 cc.-. 44 51 120 120 800 cc 120 111 Total foam after 120 seconds 780 810 300 600 650 610 300 250 Volume (cc.) of water after X min t l and 3 as defined in Table I. u uA blzend containing 27% of 0 -0 and 73% of Ci0-Cia linear secondary alkyl benzene 5 one es.

Formulations 16, '17, 19, 20 and 21 which represent embodiments of this invention generate at-a faster rate an average of 144% more foam which is 55% more stable than theaverage of those produced by Formulations 18, 22 and 23 which are outside the scope of this invention.

EXAMPLE IV v The following example was conducted in accordance with the procedure set forth in Example I. The formulations were prepared using water at 120 F. and 100 ppm. hardness.

EXAMPLE VI The following example was conducted in accordance with the procedure set forth in Eaxmple I. The tests were performed with water at 120 F., 500 ppm. hardness, and containing an additional 5% by weight gypsum.

TABLE VI Formulation No 1. 37 38 39 40 41 42 43 44 Average N 0. of carbons in alkyl chain 8.5 9.0 9.4 9.5 10.3 10.4 11.3 11.3 Actual alkyl chain carbon range 8-9 8-10 9-10 9-11 9-13 1043 Maximum carbon spread 2 3 12 2 3 5 4 4 Time (sec.) to generate specified amounts of foam" 500 cc- 19 21 120 600 cc 26 25 700 cc 40 39 s s0 71 Total foam after 120 seconds 850 880 300 Volume (cc.) of water after X minutes:

1min 20 11 153 12 14 22 153 155 2min 49 33 15s 32 42 57 156 157 min 118 102 a 99 112 12s 153 157 1 and 2 as defined in Table I.

TABLE Iv 35 Formulations 37, 38, 40, 41 and 42 which represent 1 ti N 24 25 26 27 28 29 embodiments of this invention generate at a faster rate an Fmmua average of 200% more foam which is 30% more stable A' as of carbons in alkyl 8 5 9 0 9 5 10 3 m 4 n 3 than the average of those produced by Formulations 39, f fg 55,555,555;55 j -1 -1 4 2 43 and 44 which are outside the scope of this invention. lidaximtgm tiargaon spread If; .u 2 3 2 3 5 4 lme sec. 0 genera e spec e amounts of foam: EXAMPLE VII 16 13 12 18 65 33 3 i; 3% 32, Gypsum slurries are prepared by agitating 100 parts c 61 34 29 46 of gypsum in 100 parts water. 0.25 part of potassium sul- 2 1 gfggg gg gf gg gg gggsi'gfifi: 800 9 0 9 5 660 fate and 1.0 part starch are added as an accelerator and utes: 8 9 5 7 13 retarder respectively. 0.03 part of frothing Formulation 23 23 18 20 27 Numbers 1, 3, 4 and 5 from Table I are agitated until 91 87 71 77 86 foams having a density of about 12 lbs./ft. are produced.

2 As defined in Table I.

Formulations 24, 25, 26, 27 and 28 which represent embodiments of this invention generate at a faster rate an average of 34% more foam than Formulation 29 which is outside the scope of this invention.

EXAMPLE V The following example was conducted in accordance with the procedure set forth in Example I. The formulations were prepared using water at 120 F. with 500 p.p.m. hardness.

TABLE V Formulation No 3O 31 32 33 34 35 36 Average No. of carbons in alkyl chain 8. 5 9.0 9. 5 10. 3 10. 4 11.3 13.0 Actual alkyl chain carbon range 8-9 8-10 9-10 9-11 9-13 10-13 12-14 Maximum carbon spread- 2 3 2 3 5 4 8 Time (sec.) to generate specified amounts of foam:

1 and 2 as defined in Table I.

These foams are then stirred into the various gypsum slurries. The slurries are then deposited between two layers of paper. The sheets are then cured at 300 F. until the free water has evaporated and the gypsum has set. The resultant boards are light in weight and have uniform density characteristics.

We claim:

1. In the production of gypsum board comprising the steps of preparing a fluid gypsum slurry containing a froth, depositing the slurry between two impervious barriers and heating the slurry to evaporate the water and set the gypsum, the improvement which comprises utilizing as the frothing agent an alkyl benzene sulfonate having a linear secondary alkyl side chain With an average carbon content ranging from 8.5 to 10.5 and a maximum carbon number spread of eight carbons.

2. A method according to claim 1 wherein the alkyl benzene sulfonate is utilized in amounts ranging from 0.01 to 0.1 per parts gypsum.

3. A method according to claim 1 wherein the alkyl benzene sulfonate has an average carbon number ranging from 9.5 to 10.5.

4. A method according to claim 1 wherein the alkyl benzene sulfonate has a maximum carbon number spread of 5 carbon atoms.

5. A method according to claim 1 wherein the alkyl benzene sulfonate is an alkali metal salt.

6. A method according to claim 5 wherein the alkali metal is sodium.

7. A method according to claim 1 wherein the froth is first prepared and then incorporated into the gypsum slurry.

8. A method according to claim 1 wherein the improvement comprises-utilizing the sodium salt of an alkyl benzene sulfonate having a linear secondary alkyl side chain with an average carbon content ranging from 9.5 to 10.5

References Cited UNITED STATES PATENTS 2,913,346 11/1959 Hoffman 106111 3,359,146 12/1967 Lane et a1 106111 JAMES E. POER, Primary Examiner US. Cl. X.R.

and a maximum carbon number spread of five carbon 10 106-112, 113, 114; 156-43 atoms. 

